The present invention relates generally to systems and methods for optimally positioning surgical instruments within a body cavity, for example, for performing cryosurgery. More particularly, the present invention relates to a system and apparatus for filling a body cavity, such as the uterus with a fluid, e.g., thermally conductive fluid and for facilitating surgical instrument placement at an optimal position within the body cavity, e.g., the uterus, to promote an effective and efficient surgical procedure, such as cryoablation, and for permitting removal of the surgical instrument after use.
Cryosurgery has been used for several years for the treatment and ablation of tissue for a variety of therapeutic purposes. For example, cryosurgical probes have been used for ablation of the endometrial lining of the uterus for the treatment of metrorrhagia and other disorders by freezing and killing a layer of endometrial cells. Global ablation of the endometrium is indicated to treat certain conditions wherein the entire intrauterine surface is treated in one therapy cycle. Cryoprobe placement is particularly critical in global ablation procedures in that the cryogenic effect proceeds omnidirectionally outward away from the cryoprobe tip. Accordingly, it is beneficial to optimally position the cryoprobe within the intrauterine cavity to achieve efficient global ablation. Three basic steps are required in cryoendometrial ablation, viz., (i) the introduction of a thermally conductive medium into the uterus to substantially fill the cavity for efficiently conducting heat from the endometrial lining to the cryoprobe;(ii) to place the cryoprobe within the uterus in the most effective position and activate it; and (iii) to remove the cryoprobe.
A method for necrosing endometrial cells of the uterus is disclosed in U.S. Pat. No. 3,924,628 which utilizes an expandable bladder which is inserted in a deflated condition into the uterus on the tip of a probe. After insertion into the uterus, the bladder is inflated with a gas such as nitrogen or freon which also acts as a refrigerant. As it is inflated, the bladder conforms to the interior shape of the uterine cavity. In order to conform the bladder to the shape of the uterine cavity, significant pressures are required which may be uncomfortable for the patient. The bladder also constitutes a thermal barrier to the cryogenic effect, insulating the endometrium from the nitrogen gas. Because of variations in the internal volumetric capacity of uteri within a population, it is not immediately apparent how much thermally conductive fluid is required to fill a given uterus. If fluid pressure alone is used as the indicator of a completely filled intrauterine cavity, the high pressures of distending the bladder and conforming it to the intrauterine shape reduce the relative significance of incremental pressure differences attributable to over-distending/overfilling the cavity. The bladder method therefore leads to a tendency to overfill, resulting in discomfort. As an alternative to a bladder constrained medium, the prior art has also employed unconstrained thermally conductive medium such as saline solution delivered by a catheter into the uterus.
After the thermally conductive medium has been infused into the uterus, a cryoprobe may then be placed therein. The present methods used for cryoendometrial ablation utilize ultrasound to verify the position of the cryoprobe relative to the uterus. Utilization of ultrasound adds complexity, costs and scheduling constraints to the procedure. Further, ultrasound does not guarantee that the cryoprobe will be effectively positioned in the uterus to efficiently freeze the thermally conductive medium. Actuating an improperly positioned cryoprobe fails to achieve optimal necrosing results. Accordingly, it would be beneficial to solve the problems of the prior art as set forth above.
U.S. Pat. No. 5,275,595 describes a cryosurgical probe which is cooled by a refrigeration system. Cryosurgical treatment of the uterine endometrium and other tissues is described in U.S. Pat. Nos. 3,924,628, 5,647,868 and 5,520,682 and other patents. Use of particulate microcrystalline material, for example diamond suspended in a fluid carbonyl or paraffin, as a heat transfer material is described in U.S. Pat. No. 4,764,845.
U.S. Pat. Nos. 4,016,867, 4,685,474 and 4,204,548 disclose apparatus for measuring the internal dimensions of a uterus and include a caliper-type apparatus which expands to conform to the dimensions of the uterine cavity.
The limitations of the prior art methods and apparatus for performing surgery in a body cavity using a surgical instrument with a proximal portion and a probe portion are solved by the present invention which includes a positioning assembly for positioning a distal end of the probe portion within the body cavity at a selected position relative thereto. The positioning assembly has at least one positioning element which can assume a retracted position to allow insertion of the positioning assembly into the body cavity and a deployed position in which the positioning element is displaced radially outward relative to the retracted position and relative to an axis of the probe portion when the probe portion is inserted in the body cavity. The positioning element is capable of contacting an interior surface of the body cavity to move the probe portion away from the interior surface when the positioning element is deployed.